1. Field of the Invention
The present invention relates to a method of forming a thin film pattern, and particularly to a method of forming a metal film having a fine pattern. Furthermore, the present invention relates to a method of manufacturing a thin film magnetic head having an inductive type thin film magnetic head element, and particularly to a method of forming a pole portion of an inductive type thin film magnetic head element.
2. Description of Related Art
A method of forming a thin film pattern of the present invention can be applied to formation of a high-density wiring pattern in various circuit elements, integrated circuits and the like. Sine the method is particularly suitable for forming a pole portion of an inductive type thin film magnetic head element which is faced to a magnetic record medium, a method of forming such a pole portion will be described in the following. In a thin film magnetic head used in a magnetic disk unit constituting a storage in a computer, a combination type thin film magnetic head in which an inductive type thin film magnetic head element is used as a writing element and a magnetoresistive element (MR element) is used as a reading element has made the main current.
In a combination type thin film magnetic head including a writing inductive type thin film magnetic head element stacked on a reading MR element, the inductive type thin film magnetic head comprises a bottom magnetic film serving also as a top shield for the MR reading element, a gap film, a gap film, a top magnetic film, a thin film coil supported by an insulating film made of an organic resin, and the like.
The end portions of the bottom magnetic film and the top magnetic film have respectively a bottom pole portion and a top pole portion facing each other via the gap film having a very small thickness, and a writing operation is performed by these bottom pole portion and top pole portion.
The bottom magnetic film and the top magnetic film are magnetically coupled with each other at the opposite side to the abovementioned bottom pole portion and top pole portion to form a magnetic circuit. This magnetically coupled portion is called also a back gap portion. The thin film coil is formed such that the coil is wound around the back gap portion.
In order to attain a high recording density using a thin film magnetic head of this kind, it is necessary to increase an amount of data to be recorded in unit area (surface recording density) of a magnetic disk. The surface recording density is governed by the ability of the writing element. The surface recording density can be improved by making small the gap length between the bottom pole portion and the top pole portion in the writing element. However, since shortening the gap length causes a reduction in the intensity of a magnetic flux passing through these pole portions, it is naturally limited.
Another means for improving the surface recording density is to increase the number of data tracks recordable on the magnetic disk. The number of data tracks recordable on a magnetic disk is usually represented by TPI (Tracks Per Inch).
The TPI of the writing element can be increased by making small a head size determining a width of a data track. The head size is usually called a track width of head.
Since an inductive type thin film magnetic head element performs the writing operation in the bottom and top pole portions facing each other via the gap film having a very small thickness, in order to reduce the track width of head determining a width of a data track, it is necessary to reduce a width (a size of the pole portion measured in parallel with the gap) of at least one of the bottom pole portion and the top pole portion.
In case of forming a pole portion, up to now, a photoresist film is formed and then a cut-out pattern is formed therein by a photolithography process. Next, a magnetic film containing a desired pattern of the pole portion is formed in the cut-out pattern by means of an electroplating and the like. Therefore, the accuracy of the pattern of the magnetic film including the pole portion is influenced by the performance of the photoresist film, and the resolution, focus and the like of an exposure light source. Heretofore, the head size of he pole portion has been made narrow and small by selecting a high-performance material as photoresist and shortening a wavelength of the exposure light source. However such a known method could not make a width of the pole portion smaller than a limit size determined by the optical performance of an exposing apparatus used in a photolithography process.
Furthermore, since the photoresist film is formed to have a substantially constant thickness, as a track width of head determining a width of a data track becomes smaller, the aspect ratio (height/width) of a height (thickness) of the photoresist film to a width of the cut-out pattern becomes larger. When this aspect ratio becomes large, even if a high-performance photoresist material is utilized and an exposure light source having a short wavelength is used, the cut-out pattern could not be accurately formed. In such a way, in the conventional manufacturing method, it has been considered that there would be a limit to make narrow and small a track width of head and a thin film magnetic head having a track width of 1 xcexcm or less is difficult to obtain.
Moreover, in the thin film magnetic head of the kind mentioned above, the insulating film supporting the thin film coil in such a condition that the thin film coil is supported in an insulated and isolated manner, forms a step having an abruptly increasing height. Due to this step, in a photolithography process for forming the top yoke, a photoresist is liable to be deposited have a large thickness at said step. Therefore, the top pole portion has to be formed by patterning a very thick portion of the photoresist deposited on a root of the step, and thus the aspect ratio becomes remarkably high. Due to this, a reduction in a size of the track width of head has a certain limitation.
A technique of minimizing the track width of pole portion by applying an ion beam milling process has been known. However, it is difficult to attain a track width of 1 xcexcm or less even by using such a technique. Moreover, it is difficult to mill vertically both side walls of the pole portion viewed in a direction of the track width of pole portion and both side walls are liable to form tapered faces spreading slightly wider toward the bottom. When the pole portion has such tapered faces, a problem of side fringing occurs.
In order to prevent the side walls of the pole portion from being tapered, a method of irradiating the side walls with an ion beam at a certain angle is disclosed in the specification of U.S. Pat. No. 5,438,747 issued to Krounbi et al., on Aug. 8th, 1995. However, since this method could not easily form vertical side walls of the pole portion, it is difficult to manufacture a thin film magnetic head having a track width of 1 xcexcm or less.
In addition to the above described method of forming the pole portion of the inductive type thin film magnetic head, in a method of forming a wiring pattern in various circuit elements, integrated circuits or the like, after a photoresist film has been formed on a substrate, a cut-out pattern is formed by a photolithography process and a wiring metal film having a given pattern defined by the cut-out pattern is formed. Also in such a method, it is difficult to make a line width of a metal film smaller than a limit size determined by the optical performance of an exposing apparatus used in the photolithography process. And such a problem occurs in the same way not only in case of forming a metal film pattern but also in case of forming a thin film pattern of another material.
An object of the present invention is to provide a method of forming a thin film pattern, said method being capable of forming a thin film pattern, particularly, a metal film pattern whose width is set at a very small value in high accuracy.
Another object of the present invention is to provide a method of forming a thin film pattern, said method being capable of forming a thin film pattern, particularly, a metal film pattern whose width is more narrow and smaller than the limit of an exposing apparatus used in a photolithography process.
Another object of the present invention is to provide a method of forming a thin film pattern, said method being capable of forming a thin film pattern, particularly, a metal film pattern having vertical side walls.
Another object of the present invention is to provide a method of forming a pole portion of a thin film magnetic head, said method being capable of forming a pole portion of an inductive type thin film magnetic head whose track width is set at a very small value in high accuracy, at a very small value exceeding the limit of an exposing apparatus according to necessity, or particularly at a very small value of 1 xcexcm or less.
A further object of the present invention is to provide a method of forming a pole portions of an inductive type thin film magnetic head, said pole portion having vertical side walls.
Another object of the present invention is to provide a method of manufacturing a thin film magnetic head, said method being capable of manufacturing an inductive type thin film magnetic head in which a track width of pole portion can be set at a very small value in high accuracy.
Another object of the present invention is to provide a method of manufacturing a thin film magnetic head, said method being capable of forming a pole portion having a track width narrower or smaller than a limitation due to an exposing apparatus.
Another object of the present invention is to provide a method of manufacturing a thin film magnetic head, said method being capable of forming a pole portion with a track width having a very small value of 1 xcexcm or less.
A still another object of the present invention is to provide a method of manufacturing a thin film magnetic head, said method being capable of forming a pole portion having vertical side walls.
According to the present invention, a method of forming a thin film pattern comprises the steps of:
forming a dummy pattern film on a substrate, said dummy pattern film having a shape corresponding to a shape of a desired thin film pattern to be finally formed on the substrate;
forming a frame film around the dummy pattern film;
removing said dummy pattern film to form a depressed portion having a shape corresponding to the shape of the dummy pattern film in said frame film;
forming a desired thin film pattern in the depressed portion formed in the frame film.
Furthermore, according to the present invention, a method of forming a metal film having a desired pattern comprises the steps of:
forming a first resist frame on a substrate whose at least one surface is electrically conductive, said first resist frame having a shape corresponding to said desired pattern of the metal film;
depositing a metal-plated film around said first resist frame by an electroplating process using said electrically conductive surface of the substrate as an electrode;
removing said first resist frame with said metal-plated film being remained to form a depressed portion having a shape corresponding to said shape of the first resist frame; and
forming a metal film having said desired pattern within the depressed portion formed by removing said first resist frame.
In this way, in the methods of forming a metal film according to the present invention, the first resist frame with the pattern corresponding to the desired pattern is first formed on a substrate. In comparison with a case of forming a cut-out pattern in a resist film or a case of an ion beam milling process, this process can reduce the width or adjust the shape of the first resist frame by applying an ashing process to it. Then, it is possible to make the resist width more narrow and smaller in the first resist frame than a limitation imposed by an exposing apparatus. Additionally, it is possible to make vertical the side walls of the first resist frame. When the substrate is made of an electrically insulating material, an electrically conductive film may be applied on the surface for the later electroplating process.
Next, the metal-plated film is formed around said first resist frame. Next, the first resist frame is removed while said metal-plated film is remained. Due to this, the desired pattern can be formed by removing the first resist frame. In the conventional method, said pattern is formed as the cut-out pattern of the photoresist film. The depressed portion obtained by removing the first resist frame has a shape which is obtained by duplicating the shape of the first resist frame, and therefore the depressed portion has an accurately defined shape and its side walls are optimized as vertical walls.
Next, the metal film is formed within the depressed portion formed by removing the first resist frame. As described above, since the depressed portion formed by removing the first resist frame has the shape which is a duplication of that of the first resist frame and has the vertical side walls, the width (line width) of the metal film formed within said depressed portion can be made smaller than the limitation imposed by the exposing apparatus. Additionally, the side walls of the metal film can be made vertical.
It is particularly preferable that before forming the metal film within the depressed portion obtained by removing the first resist frame, a second resist frame having an opening which surrounds the depressed portion formed by removing said first resist frame and is communicated or aligned with the depressed portion is formed on the metal-plated film, and then the metal film is formed within a space defined by the depressed portion as well as the opening formed in the second resist frame. Such a second resist frame has a function of preventing the metal film from being formed on the metal-plated film upon forming the metal film by plating, and can make the aspect ratio of the metal film higher by forming the metal film such that the not only the depressed portion formed in the metal-plated film is filled with the metal, but also at least a part of the opening formed in the second resist frame is filled with the metal. Furthermore, by making a size of the opening formed in the second resist frame larger than a size of the depressed portion formed in the metal-plated film, it is possible to form a metal film having a T-shaped cross section, and such a structure is particularly useful as the structure of a pole in a thin film magnetic head.
The present invention also relates to a method of forming a pole portion of an inductive type thin film magnetic head. In a method of forming a pole portion of an inductive type thin film magnetic head according to the present invention, first a first resist frame is formed on a substrate at least a surface of which is electrically conductive, a shape of said first resist film corresponding to a desired pattern of a pole portion to be finally formed. According to this process, differently from a case of forming a cut-out pattern in a resist film or a case of an ion beam milling process, it is possible to make a width of the first resist film more narrow and to adjust its shape by an ashing process. Therefore, the first resist frame can have a high aspect ratio and a width of the resist frame can be made more narrow and smaller than the limitation imposed by an exposing apparatus. Concretely, a width of the resist frame can be set at a very small value of 1 xcexcm or less. Additionally, the first resist frame having a very small size can have vertical side walls.
Next, after a metal-plated film has been formed by electroplating around said first resist frame, said first resist frame is removed and a depressed portion is formed in the metal-plated film. In this manner, a desired pattern which has been by a cut-out pattern of a photoresist film in the conventional method can now be formed as the depressed portion obtained by removing the first resist frame, and since the depressed portion has a shape which is a duplication of the shape of the first resist frame, the depressed portion can have a very small width and can have vertical side walls.
Next, a magnetic film constituting a pole portion is formed within said depressed portion obtained by removing the first resist frame. In this way, it is possible to form the pole portion having a very small width which is smaller than the limitation imposed by an exposing apparatus, and having vertical side walls. Concretely, the width of a pole portion can be set at a very small value of 1 xcexcm or less.
An aspect ratio of the pole portion may be further increased by carrying out an additional process, in which before forming the magnetic film within the depressed portion obtained by removing the first resist frame, a second resist frame having an opening which surrounds the depressed portion obtained by removing the first resist frame is formed on the metal-plated film and said magnetic film is formed within the depressed portion of the first resist frame as well as within the opening of the second resist frame. It should be noted that by making a size of the opening formed in the second resist frame larger than a size of the depressed portion formed in the metal-plated film, it is possible to form a pole portion having a T-shaped cross section.
The present invention also relates to a method of manufacturing a thin film magnetic head having at least a writing inductive type thin film magnetic head element. An inductive type thin film magnetic head element to be formed by the method of the present invention comprises a first magnetic film having a first pole portion, a gap film, a second magnetic film with a second pole portion which is faced with the first pole portion of said first magnetic film via said gap film, said second magnetic film being magnetically coupled with said first magnetic film at a back gap part opposite to said second pole portion, and a thin film coil having a portion passing through a magnetic path formed by said first and second magnetic films.
According to the invention, in a method of manufacturing such a thin film magnetic head, after forming said first magnetic film and said gap film, a first resist frame having a pattern corresponding to a pattern of the second magnetic film is formed on said gap film. According to this process, differently from a case of forming a cut-out pattern in a resist film or a case of an ion beam milling process, it is possible to reduce a width of the pattern of the first resist frame more narrow and to adjust the shape of the first resist frame by an ashing process and the like. Therefore, it is possible to make the aspect ratio high and make the width more narrow and smaller than the limitation imposed by an exposing apparatus. Concretely, a width of the resist frame in a pole portion can be set at a very small value of 1 xcexcm or less, and the side walls can be made vertical. When the gap film is made of an electrically insulating material, an electrically conductive film which is required in a later electroplating may be deposited on the gap film.
Next, after depositing a metal-plated film around the first resist frame by the electroplating, a depressed portion is formed in the metal-plated film by removing the first resist frame. Then, a desired pattern which has been formed by a cut-out pattern of a photoresist film in the conventional method can now be formed as the depressed portion obtained by removing the first resist frame, and since the depressed portion has a shape which is a duplication of the shape of the first resist frame, the depressed portion can have a very small width and can have vertical side walls.
Next, a second magnetic film including a second pole portion is formed within the depressed portion formed by removing the first resist frame. The pattern of the depressed portion formed by removing the first resist frame has the shape which is a duplication of that of the first resist frame and the side walls are vertical. Accordingly, the pattern of the second magnetic film formed within the depressed portion also corresponds to the pattern of the first resist frame, and a width of the second pole portion can be made more narrow and smaller than the limitation imposed by an exposing apparatus. Concretely, a width of the second pole portion can be set to a very small value of 1 xcexcm or less. Additionally, the side walls of the second pole portion can be made vertical.
Before forming the second magnetic film within the depressed portion obtained by removing the first resist frame, an additional process may be performed such that a second resist frame having an opening which surrounds the depressed portion obtained by removing the first resist frame is formed on the metal-plated film and said second magnetic film can be formed within the depressed portion formed in said metal-plated film as well as within the opening formed in the second resist frame.
In the method of manufacturing a thin film magnetic head according to the present invention, a reading magnetoresistive element may be formed in addition to the writing inductive type thin film magnetic head element. The reading magnetoresistive element comprises a first shield film, a second shield film, and an MR film which is embedded in a shield gap film between the first shield film and the second shield film. In the method of manufacturing a thin film magnetic head according to the present invention, the magnetoresistive element may be first formed on the substrate, and then the inductive type thin film magnetic head element may be formed on the magnetoresistive element, or the inductive type thin film magnetic head element may be first formed on the substrate and then the magnetoresistive element may be formed on the inductive type thin film magnetic head.